Vehicle coolant pumps, often referred to as water pumps, are used to circulate coolant through the cooling passages of an engine block. They are generally operated by a driving member in the form of a pulley, which is in turn powered by a drive belt that runs off of the engine. It is necessary, of course, that the impeller of the pump be in communication with the coolant, in order to circulate it. The impeller is usually internal to a housing which is attached to the engine block and which encloses a space that communicates with the engine block cooling passages. A shaft or other member must be physically connected from the pulley to the impeller, which necessitates an opening physically through the housing. That opening must be sealed against the egress of coolant. The seal is highly stressed by the rapid rubbing rotation of the shaft that it surrounds, and by the heat of the coolant, coolant which may well contain abrasive particles, and will inevitably wear. The U.S. Pat. No. 3,632,220 to Lansinger et al illustrates well the problems with this conventional type of coolant pump. A generally cylindrical housing 9a, which stands out from the engine block 9, has a shaft 11 supported by a bearing 12 passing through it. The shaft 11 is sealed with a complex seal assembly, generally referred to as a cartridge seal, made up of two seal members 26 and 27 spring loaded against one another. Although it is not numbered, one skilled in the art will recognize a weep hole through the housing 9a opening to the ambient to vent the coolant that will invariably leak past the cartridge seal. In addition, a strong, and therefore highly frictional, bearing seal must be provided at the inner end of the bearing 12 to exclude leaking coolant from entering the bearing. Leaking coolant is the major cause of water pump bearing failure. It will also be noted that the pump disclosed is not particularly axially compact, as measured along the axis of the shaft 11. The housing 9a extends out from, not into, the engine block, and the bearing is spaced axially far away from the pump impeller 21. The complexity of the cartridge seal, as well as the necessity of venting the leaking coolant, all militate against making the pump more axially compact by moving the cartridge seal and bearing back inside the block, where they would not be so accessible or easily vented.
It is known, in general, to operate a pump impeller located on one side of a closure with a driver located on the other side of the closure by the use of opposed magnetic elements on the pump impeller and driver. This avoids passing a shaft physically through the closure, and thus no seal is necessary around the shaft. Numerous patents exist in the field of magnetic drive pumps, all of which incorporate the basic feature just described, with the consequent advantage of avoiding a seal. They are directed to various narrow and specific structures, none of which one skilled in the art could apply, without the application of inventive effort, to use as a vehicle coolant pump. Most involve very different environments and problems, such as pumps to be used with a large tank of corrosive chemicals, where space is not a critical factor.
For example, the U.S. Pat. No. 4,304,532 to McCry shows such a pump with an impeller 38 operated by a driver 20 which that is in turn powered by a shaft 18 from a motor 12. There are no particular space limitations in such an environment, and the motor 12 can be axially far removed from the impeller 38 with no problem. Such is not the case in the cramped environment where a vehicle coolant pump is to be used. More importantly, a vehicle coolant pump cannot be powered directly by a separate power source like a motor, but must be run indirectly from the vehicle engine with a belt and pulley. That pulley must be rotatably supported and axially and radially located relative to the pump impeller. The motor 12 in McCry is large and stable, and has its own internal bearings, so it is a simple matter to rotatably support the shaft 18 and driver 20 relative to the impeller 38. Similarly usable structure is just not available in the environment of a vehicle coolant pump. Other patents illustrate the same point. The U.S. Pat. No. 3,802,804 to Zimmermann shows another magnetic tank pump, again with a large motor 40 to support and locate a driver 38 relative to an impeller 35, all occupying a relatively large space in an environment where space is not a limitation. Other patents in the same field, such as the U.S. Pat. No. 4,115,040 to Knorr, do not disclose anything about bearings to support the driver and impeller, taking it as a given that there would be more than sufficient space and structure in the particular environment to provide them.